Post-flow is the amount of time argon will continue to flow through the torch head after the welding process is completed. A good rule of thumb is 1 second of post-flow for every 10 amps of welding current. If you are welding at 50 amps you will need 5 seconds of post-flow. On my TIG Diversion 180 post-flow is calculated internally inside the machine, but with the Dynasty 200 and some older Miller welding machines you can set the post-flow per the amount of current with a digital knob. Post-flow is very important because without it the tungsten rod at the end of the TIG torch will become contaminated with oxides and then when you start the weld process the oxides will then melt off the tungsten and contaminate the weld.